1) He gave them all together one hundred dollars.2) He gave them all one hundred dollars. 3) He gave them one hundred dollars.4) He gave them one hundred dollars altogether.

5) He gave them one hundred dollars jointly.

Is '5' correct?

In which of the sentences is it possible that he has given different sums to different people and the sum total is one hundred dollars? (for example: He gave 20 dollars to Jack. He gave 50 dollars to George. He gave 20 dollars to Keith. And he gave ten dollars to Harry. In total, he gave them one hundred dollars.)

In which case is it possible that we have a series of payments to the group as a whole?

In which case is it possible that a lump sum was given to the group as a whole?

Navi, in your example number 1, the meaning you're looking for can be made clear by adding commas, like so:

He gave them, all together, one hundred dollars.
OR
All together, he gave them one hundred dollars.

It's a little ambiguous, I admit, but it will work.
There have been a few discussions on this site about the value of commas. They are very important.
By the way, I notice the title of this discussion is "altogether", which is altogether different from all together (now).

Also, your example number 3 (he gave them one hundred dollars) states clearly that the group, as a whole, received the amount.

My readings:
1. This is an extremely ungainly and unlikely construction. I have difficulty extracting meaning from it, particularly as I listen to these posts, and I cannot distinguish between "all together" and "altogether" without reading word by word.

2. My intuitive reading is that each one received one hundred dollars.

3. He gave the whole group one hundred dollars.

4. The total sum he gave them was one hundred dollars. This can either mean that he gave the whole group several sums of money totalling one hundred dollars or he gave each member of the group a sum of money and the total amount given was one hundred dollars.
5. This is a little unusual, but unambiguous.